1. Biomedicine 
a, Current Situation Fundamental man-in-the-sea 
technology is bio-engineering oriented and is par- 
ticularly concerned with human functions and 
performance undersea. Devices, equipment, and 
materials must be provided which (1) enable man 
to withstand changes in pressure and temperature 
associated with increasing depth for extended and 
repeated periods, (2) accommodate his sensory 
requirements to maintain adequate visibility, 
orientation, feel, and hearing, and (3) provide him 
with directional and locator capability, mobility, 
and tools. 
Although experimental dives have been made to 
depths in excess of 1,000 feet, current technology 
restricts operation to approximately 600 feet for 
relatively short intervals. 
Scuba (untethered diving wherein the diver 
carries his life support system, maintains near 
neutral buoyancy, and enjoys nearly complete 
dexterity) currently is most useful for shallow 
short-duration dives. 
Normally in commercial operations, divers are 
tethered to the surface. The diver receives gas from 
the surface and maintains communication with top- 
side personnel who calculate his decompression 
time. Diver bottom time is increased over scuba. 
Deep diving systems often are employed when 
operations require dives in excess of 300 feet for 
several hours. 
The nucleus of the deep diving system is a 
pressure vessel that serves as an elevator trans- 
porting divers to the underwater site. Many such 
systems provide for mating the personnel trans- 
fer capsule with a deck decompression chamber 
so divers can decompress in relative comfort. Deep 
diving systems eliminate in-water decompression 
and provide backup life support to enhance safety. 
If a man is to work for a long period at a 
particular depth he must adapt physiologically. 
Prolonged living under increased pressures has 
been demonstrated in such saturated diving experi- 
ments as the U.S. Navy’s Sealab and the Cousteau 
Conshelf. Using this technique, after about 24 
hours a diver has absorbed all the gas his system 
will at that depth, and the time he must spend in 
decompression remains the same. Therefore, the 
longer the diver stays, the greater his productive 
time compared to decompression time. 
Saturation diving has been employed in the 
open sea to about 650 feet and probably will be 
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extended beyond 1,200 feet in the near future. 
Saturation diving, however, requires expensive 
special life support equipment and instrumenta- 
tion and so is not economical for most current 
operations. 
Special breathing mixtures pose a host of 
physiological and bio-engineering problems. 
(1.) Physiological Toxicity of breathing gases, 
individually and combined, for greater depths is 
not established firmly—particularly for extended 
periods of continuous exposure. 
The total effect upon respiration and metabo- 
lism of operating at greater depths imposes severe 
restrictions on such basic operational parameters 
as rate of ascent, diving depth, duration, and work 
accomplished. For example, the breathing appara- 
tus must precisely measure and control partial 
pressure of oxygen when the concentration is well 
below one per cent. 
Gas density and sound velocity change with gas 
composition and distort the voice, making com- 
munication difficult. 
(2.) Bio-engineering Essentially all engineering 
designs must be revised to accommodate variations 
in density, viscosity, thermal conductivity, and 
other properties of gas mixtures employed. Mate- 
rials, equipment, and instrumentation are subject 
to serious malfunction because of these variations. 
It is a specialized engineering problem, and discre- 
tion must be exercised in employing off-the-shelf 
hardware. 
The Navy’s Biomedical Engineering Program is 
conducted as a coordinated effort of several 
groups. The Deep Submergence Systems Project 
and the Office of the Supervisor of Salvage are 
involved principally with hardware development 
for near-term application. 
The Underwater Bio-Sciences Research Program 
of the Bureau of Medicine and Surgery is a 
comprehensive five-year plan for basic research in 
support of Navy underwater operational require- 
ments. Concurrent human factors research is 
directed by the Office of Naval Research. The 
overall plan was issued by the Chief of Naval 
Development, who enlisted the aid of several 
organizations and the academic community. 
b. Future Needs The following Navy programs in 
underwater biomedical research and development 
are designed to meet future biomedical needs. 
